Means for starting free piston engines



Dec. 9, 1941. l H. JNICKE 2,265,285

MEANS FOR STARTING FREE PISTON .ENGINES Original Filed May 17, 1934 2 Sheets-Sheet l l n n f l Dec. 9; 1941. H. JNICKE 2,265,285

MEANS FOR STARTING FREE PISTON ENGINES Original Filed May 17, 1934 2 Sheets-Sheet 2 l WwW/L- `application for U. B. Letters Patent Patented Dec. 9, 1941 Hermann Jnicke, Dresden, Germany, assignor to Hugo Junkers, of Landhaus Junkers, Bayrisch- Zell, Oberbayern. Germany: Therese Junkers,

o adminlstratrlx oi' the estate of Hugo Junkers,

decGavled original application 4May 17, 1934, serai No.

Divided and this application June 21,

1940, serial No. 341,680. 1n Germany May z3,

(ci. 23o-5s) y 6 Claims.

My invention relates to means for starting free piston engines. It is an object of my invention to provide improved means for starting such en- Eines. v

'I'his application is a division of my copending 726,167, filed May 17, 1934.-

Ser. No.

rocating bodies and charged with' the necessary starting energy, this device reciprocating during In free piston engines provided with springs 'A connected'to the reciprocating bodies of the engine and serving for storing, during the working stroke, the energy required for compressing the charge in the motor cylinder and' feeding it back during the return strokeI the engine is started by placing the springs under tension by means of an outer force and releasing the reciprocating'bodies. This arrangement, however. involves the drawback that the springs used as permanently operating energy storers must be very large and heavy.

It has been further proposed to provide an energy -storing device comprising springs merely for starting purposes,the device being automatically coupled to the reciprocatingl bodies, while the springs are placed under tension, and being disengaged from these bodies after having re-fed the stored energy during the first compression stroke.

The principal dilculty, however. with the starting meth-:ids and devices hitherto known resides in that they impart to the reciprocating bodies only a single impulse, so that during the second part of the initial reciprocation, i. e. by the end of the first working stroke operating conditions must be provided which guarantee the further operation of the engine under ordinary conditions on the motor side as well as on the compressor side. With the spring starters hitherto known it is valtogether impossible to obtain in all stages of a ymulti-stage free piston compressor already during the first compression stroke sufficiently high pressures for obtaining from the compressor during the subsequent reat least the'first stroke in such manner that only the storer receives, stores and feeds back the energy required for maintaining the reciprocation of the reciprocating bodies. while the energy consumer, for instance the compressor, reciprocates idle. A Thereafterthe receiving and feeding of energy is transferred gradually, i. e. during a plurality of strokes, from the storer to the energy consumer by gradually diminishing the energy to be stored and fed back by the storer, and correspondingly increasing the amounts of energy delivered'to the energy consumer and refed from the consumer to the reciprocating bodies, until the storer is altogether released and merely'runs idle 'I'he gradual loading of the energy consumer maybe carried out automatically in dependency upon the unloading of the storer, or vice versa, the storer may be gradually unloaded in an automatic manner in dependency upon the increasing loading of the energy consumer. After reaching normal operation, the starting storer may further reciprocate turn stroke the energy required for compressing the charge in the motor cylinder so th'at the engine will not come to a standstill. In engines of this kind means should be provided for extending the starting period from a plurality of strokes before changing Iover to normal operation.

It is an object of my invention to provide starting means which avoid the drawbacks discussed above and eilect starting in a safe manner and with a minimum demand of energy.

In order to accomplish this I provide a meidle or may be disconnected from the reciprocating bodies.

Preferably the reciprocating bodies are arrested during the charging of the storers by v means of locking devices, the starting stroke be*- ginning after these locking devices have been released.

In order to avoid an energy discharge during the initial strokes and to reduce the amount of energy required for starting, blocking devices, for instance valves, may be inserted in the delivery pipe of the engine or between the stages of a multi-stage compressor, such -blocking devices or valves being preferablyopened gradually during the changing over to normal operation.

The amount of starting energyof the storing device may be further reduced by decreasing the resistances to be overcome during the starting stroke, for instance by reducing the gas volume to be compressed in the motor cylinder by. discharging part of the charge by means of suitable controlling devices, preferably operating in dependency upon the charging over of the transfer of energy from the storing device to the energy consumer. If desired, a control of the fuel fed to the motor cylinder may be connected with these devices, for instance by adjusting the fuel delivery in such manner that a small amount of fuel is vfed during starting, the amount of fuel being gradually increased during the changing over.

chanical energy storer coupled with .the recip- 55. In the drawings aillxed to this specification and `1l is a casingrotatable which"l press Referring to the drawings, and rst to Fig. 1, the free piston engine includes two reciprocating bodies, each comprising a motor piston I and a compressor piston 2, reciprocating in opposite directions in a motor cylinder II and compressor with the same reference numerals.

cylinders I2, respectively. l and 5 are inlet and 20/ exhaust ports provided in the wall of the motor cylinder II. The compressor cylinders I2 are provided with suction valves 1 and pressure valves 8. In order to secure exact opposite reciprocation, the reciprocating bodies are 25 coupled with each other by means 6I a coupling device comprising toothed racks I4, Il' each connected to one of the compressor pistons 2, and a lpinion I5 (shown in Fig. 3) engaging the toothed racks and rotatably secured in the' engine 30 casnginot shown). ,I6 is an inlet nozzle for delivering fuel into the cylinder II. The'reciprocating bodies can be arrested by means of a locking device comprising a latch I8 releasable by means of a spring loaded hand lever I9 and 35 cooperating with a locking tooth I1' provided on the rack I4. With the position of the locking device shown in 1 the reciprocating bodies are 'locked approximately in their outer dead center positions.

The connecting pipes 3l are connected to the discharge pipe 3I, leading to the consumer (not shown), through a container 50 which is so dimensioned as to be charged to normal operat- A ing pressure within a predetermined number of strokes following the .start of the engine. A valve 32 loaded by a spring 33 is provided in the discharge pipe 3I ina manner such that it will open when normal pressure has been established in the container 58. Referring now to Figs. 1, 2 and 3, the pinion I5 of the coupling gear has'a shaft ill to which th'e movablenember 6I Lof a coupling is secured so as to be axially displaceable' by means of a hand lever BIc. The other coupling member Ilb is connected to a toothed wheel 62 engaging a toothed wheel 63, the shaft il of which carries a cam disc 85 comprising a plurality of cams 86 uniformly distributed along a circumference thereof. The step-downl ratio of the toothed wheels 62 and B3 and the shape of the cams 6B are chosen in a manner such that the angle of rotation of the wheel 33 and the cam disc B5 corresponding to the maximum stroke of the recip- 65 rocating bodies is approximately equal to the angle corresponding to the arc occupied by the inclined portions 61 of the cam', cylindrical por.- tions 68 being provided between the 61:. occupying angles of at least the same magnitude. 70

about the shaft i4 of the disc 55 and providedV with suitably arranged extensions 18a, in which springs 1I are arranged sliding members 12 provided with rollers 13 against the circumference of the cam 15 ascenso disc 65. The force exerted by the springs 1I on the camdisc 55 tends to rotate the disc in the direction of the arrow a. rocked by means of a hand lever 14'- provided with a spring-loaded latch 11 adapted to engage two recesses 15 and 16 formed in the arc-shaped portion of a stationary member 18, so that the casing 10 may be locked in -two positions corresponding to the engagement of the latch 11 and the recesses 15 and 1B, respectively. The position shown in'Flg'. 2 in which the latch 11 engages the recess 15, corresponds to starting, the other position, in which the latch 11 engages the recess 16, corresponds to normal running; is

a pin suitably secured to the casing 10 and connected to a member 33a, against which the spring 33 abuts, by means of suitably arranged links 8l, 83 and a crank lever 82 pivoted to a stationary member 8Ia, so that the tension of the spring andthereby the force exerted by the spring on the valve 32 are varied in accordance with the position of the casing 1li. Obviously this force is small when the casing is in its starting position shown in Fig. 2, and increases to a value balancing the normal pressure existing in the A pressure chambers of the engine, when the casing is rocked into the normal running position, in which the latch 11 engages the recess 16.

The starting device shown in the drawings operates as follows:

In order to start the engine, the casing 1D is positionedy as. shown in Fig. 2, the latch 11 en-V 15, and the coupling 6I is brought to engagement by suitably rocking the lever 6Ic. Thereafter the reciprocating bodies are brought into `starting position, for instance by means of a hand crank applied to the square end 68 of the shaft 6l), so that by suitable rotation the-crank pin I5 is rotated 'and the racks I4, Il' are shifted to bring the free pistons into their outer dead centre positions. By` this rotation of the shaft 60 the cam disc 65 is rotated in the direction of the arrow b shown in Fig. 2, Aso that the springs 1l arecompressed bythe cams 66. Now the free pistons are released, for instance by releasing the locking device I8, I9 shown in Fig. l, and in consequence thereof the springs 1I rotate the cam`disc 65 in the direction of the arrow a shown in Fig. 2, which is transferred to the free pistons by means of the coupling gear Il, II, I5, so as to cause the pistons to approach each other and to compress n the charge in the motor cylinder. At the end of this inwardv stroke) the charge is ignited Aand during the following outward stroke the springs 1I are compressed again, the compressor running idle,

gaging the recess since the spring 33 of the valve 3 2 is not compressed. After some starting strokes the casing 1B is slowly rocked in the direction of the arrow b (shown in Fig. 2) by .-means of the hand lever 14, so that the springs 1I are gradually unloaded.

Simultaneously with the displacement of the casing 10 the tension of the spring 33 of the pressure regulating valve 32 inserted in the supply pipingis varied, through rods 8|, 82 and 83, in such a manner that, beginning with a small starting value, this loa'd gradually increases. In this manner the compressor starts to operate against a small resistance, i. e. it mustv take up only littleenergy, while in the further course of the starting process this work gradually increases, until ilnally the storer ceases to take up any energy, which is taken up completely by the compressor. When the other end position of the The casing 10 can be ranged for operation in a motor cylinder and a to the free piston the energy required forfmaincasing 'l0 is reached, in which the latch 'I1 engages the recess 16, the engine is running in normal operating condition and the starting device runs idle, the rollers 13 engaging only the cylindrical portions 68 of the cam disc 65. After the changing over from starting to normalrunning the coupling 6I ay be disengaged in order to stop the starting device.

In the device shown in the drawings thecompressor is gradually loaded in dependency upon the unloading of `the storing device. If desired, however, the storing device might be unloaded in dependency on the gradual loading of the compressors, for instance by rocking the casing 10 by means of a piston influenced by the gradually increasing pressure in the compressor chambers. y

I wish it to be understood that I do not desire to be limited to the exactdtails of construction shown and described, for obvious modifications will occur to a personfskilled in the art.

I claim: j

1. A free pistonengine, comprising in combination, a free piston, including a motoi piston arcompressor piston arranged for operation in a compressor cylinder, a mechanical energy storer adapted to supply, during several initial strokes,

taining the reciprocation thereof,V means for gradually unloading said energy storer until it runs idle in such manner that it is partly unloaded during each stroke leading' to a compression of the motor charge, but is reloaded, during each stroke allowing said charge to expand, up to a value which is somewhat lower than the value existing at the beginning of the preceding stroke, said energy storer comprising a spring, said spring abutting, on the one hand, against an abutment, and, on the` other hand, against a movable part' adapted to follow, at least during the initial strokes, the movement of the free piston, said abutment being so adjustable that the energy, which with each stroke following a stroke due to the action of the spring, is returned by the free piston to the spring, is gradually reduced, and means connected with the abutment. said lastnamed means adjusting the compressor, in. dependency upon the adjustment of said abutment, for an output gradually increasing from zero to 50 normal output in proportion to the unloading of the energy storer.

2. A free piston engine, comprising in combination, a free piston including a motor piston arranged for operation in a motor cylinder and a compressor piston arranged for operation in a compressor cylinder', a mechanical energy storer adapted to supply, during several initial strokes, to the free piston the energy required for maintaining the reciprocation thereof, means for gradually unloading said energy storer until it runs yidle in such manner that it is partly unloaded during each stroke leading to a compression of the motor charge, but is reloaded, during each stroke allowing said charge to expand, up to a value which is somewhat lower than the value existing at the beginning of the preceding stroke, said energy storer comprising a spring, said spring abutting, on the one hand, against an abutment, and, on the other hand, against a movable part adapted to follow, at least during the initial strokes, the movement of the free piston, said abutment being so adjustable that the energy.

which with each stroke following a stroke due to 75 the action of the spring, is returned by the free l piston to the spring, is gradually reduced, and

means connected with the abutment, said last named lmeans adjusting the compressor in dependency upon the adjustment of the abutment, for an output gradually increasing from zero to and means for rendering said locking means inoperative.

3. In a free piston engine according to claim 1,

a cam dise mountedl for oscillation, means for coupling this cam disc with the free piston so that the cam disc performs the oscillatory movement corresponding, or directly opposed, to the reciprocation of the free piston, the spring abutment being so arranged that it may be rocked about the shaft of the cam disc, the spring abutting, on the one hand, against said abutment and, on the other hand, against acam of the cam disc, said latter abutment being so provided that ,coupling this cam disc with the free piston so that the cam disc performs this oscillatory movement corresponding, or directly opposed, to the reciprocation of the free piston, the spring abutting, on th'e onehand, against said abutment and,

',pn the other hand, against a cam of the cam disc, said latter abutment being so provided that the force of the spring acting against the ank of the cam'l tends to rock the cam about the shaft of the cam disc, and means for'coupling the cam disc with the free piston, said means including a disengageable coupling device.

5. In a free piston engine according to claim 1, a cam disc mounted for oscillation, means for coupling this cam disc with the free piston so that the cam disc performs the oscillatory movement corresponding, or directly opposed, to the reciprocation of the free piston, the spring abutment being so arranged that it may be rocked about the shaft of the cam disc, the spring abutting on the one hand, against said abutment and, on the .other hand, against a cam of the cam disc, said latter abutment being so provided that the force of the spring acting against the flank of the cam tends to rock the cam about the shaft of the cam disc, said cam disc being so provided, that a part of its circumference is formed by the flank of the cam, and an adjacent part is formed by a circular portion about lts rocking axis, the spring abutment arranged for oscillation about the axis of the cam disc being provided in a manner such that when the camdisc reciprocates, the abutment member transmitting the force of the spring onto the cam disc, reciprocates when, in the beginning of the starting operation, the Vabutment is in its one end position, solely along the cam flank, when the abutment is in a medium position, partly along the cam flank and partly along the circular portion, and when, at the end of the starting process, the abutment is in its other end position, only on the circular portion.

6. In a free piston engine according to claim 1, a valve variably loaded for closing provided in the outlet from the compressor and adapted to aord passage only when the compressor end pressure has-reached the amount corresponding to the load of the valve; means for connecting the rockable abutment of the energy storer spring with the member for loading the valve in a, manner such that this loading is gradually increased up to an `amount corresponding to the normal compressor end pressure, when the abutment is rocked from its initial position, corresponding to a -fully loaded energy storer, into its end position, corresponding to a completely unloaded energy 5 storer. X HERMANN JANICE. 

